Test fails with mutex lock fail?

Has anyone seen anything like this?

RESULT: PASSED (1 passes, 0 failures, 0 errors, 0 skipped, 0 expected
failures, 0 unexpected successes)
terminating with uncaught exception of type std::__1::system_error: mutex
lock failed: Invalid argument
[TestDataFormatterVarScriptFormatting.py FAILED]

It shows up occasionally on our buildbot runs, on different tests. I've
never seen it when running locally.